1. Field of the Invention
The invention generally relates to bacteria that are capable of producing biofuel from waste. In particular, the invention provides a novel clostridial species (Clostridium ragsdalei) having the identifying characteristics of ATCC No. BAA-622) and a method of synthesizing ethanol and other useful products from CO using the clostridia species.
2. Background of the Invention
It was not until the petroleum crises of the 1970's that the U.S. government started funding more initiatives to find a way to develop renewable resources to alleviate the country's dependence on oil imports (Klass, 1998). It was also then when the government had a renewed interest in biobased solvent production for gasoline blending. One of particular interest and even more so recently, is bioethanol (ethanol from biomass).
Currently the major mode of bioethanol production is through direct fermentation, which accounts for 90% of the ethanol output in the U.S. (Licht, 2001). Direct fermentation is the process in which a saccharolytic microorganism, such as a yeast or bacteria, converts sugars to ethanol. These sugars may be simple (i.e. glucose) or complex (i.e. starch, cellulose, hemicellulose). Corn starch is the primary substrate used in ethanol producing plants today. Other than corn starch, lignocellulosic biomass (i.e. grasses, small trees, paper waste, saw dust) is also being researched as a substrate for this process. Lignocellulose is comprised of cellulose, hemicellulose, pectin, and lignin. The difficulty with the direct fermentation of lignocellulosic biomass is that added pretreatment processes are necessary to break down the biomass into its individual components before microorganismal utilization. This adds more cost in the areas of materials, plant design, waste management, etc
In an attempt to make the most out the resources available for the production of fuel ethanol, alternative methods are being examined. One of these alternative methods is indirect fermentation. Indirect fermentation is the process in which lignocellulosic biomass is pyrolyzed (burned to produce gases) and the gases produced are converted to ethanol by bacteria. The gases produced are generally termed synthesis gas. Synthesis gas (C—H2—CO2), a product of pyrolyzed biomass or coal, has been and is currently being recognized for its potential role in the indirect fermentation of biomass to fuel alcohol (Zeikus, 1980, Bredwell et. al., 1980).
Anaerobic microorganisms such as acetogenic bacteria offer a viable route to convert syngas to useful products, in particular to liquid biofuels such as ethanol. Such bacteria catalyze the conversion of syngas with higher specificity, higher yields and lower energy costs than can be attained using chemical processes (Vega et al, 1990; Phillips et al., 1994). Several microorganisms capable of producing biofuels from waste gases and other substrates have been identified:
Three strains of acetogens (Drake, 1994) have been described for use in the production of liquid fuels from syngas: Butyribacterium methylotrophicum (Grethlein et al., 1990; Jain et al., 1994b); Clostridium autoethanogenum (Abrini et al., 1994); Clostridium ljungdahlii (Arora et al, 1995; Barik et al., 1988; Barik et al. 1990; and Tanner et al., 1993). Of these, Clostridium ljungdahlii and Clostridium autoethanogenum are known to convert CO to ethanol.
U.S. Pat. No. 5,173,429 to Gaddy et al. discloses Clostridium ljungdahlii ATCC No. 49587, an anaerobic microorganism that produces ethanol and acetate from CO and H2O and/or CO2 and H2 in synthesis gas.
U.S. Pat. No. 5,192,673 to Jain et al. discloses a mutant strain of Clostridium acetobytylicum and a process for making butanol with the strain.
U.S. Pat. No. 5,593,886 to Gaddy et al. discloses Clostridium ljungdahlii ATCC No. 55380. This microorganism can anaerobically produce acetate and ethanol using waste gas (e.g. carbon black waste gas) as a substrate.
U.S. Pat. No. 5,807,722 to Gaddy et al. discloses a method and apparatus for converting waste gases into useful products such as organic acids and alcohols using anaerobic bacteria, such as Clostridium ljungdahlii ATCC No. 55380.
U.S. Pat. No. 6,136,577 to Gaddy et al. discloses a method and apparatus for converting waste gases into useful products such as organic acids and alcohols (particularly ethanol) using anaerobic bacteria, such as Clostridium ljungdahlii ATCC Nos. 55988 and 55989.
U.S. Pat. No. 6,136,577 to Gaddy et al. discloses a method and apparatus for converting waste gases into useful products such as organic acids and alcohols (particularly acetic acid) using anaerobic strains of Clostridium ljungdahlii. 
U.S. Pat. No. 6,753,170 to Gaddy et al. discloses an anaerobic microbial fermentation process for the production of acetic acid.
Other strains of aceotgens have also been described for use in the production of liquid fuels from synthesis gas, e.g.: Butyribacterium methylotrophicum (Grethlein et al., 1990, Appl. Biochem. Biotech. 24/24:875-884); and Clostridium autoethanogenum (Abrini et al., 1994, Arch. Microbiol. 161:345-351).
There remains an ongoing need to discover and develop additional microorganisms that are capable of producing useful products such as biofuels via fermentation. In particular, it would be advantageous to provide microbes that are robust, relatively easy to culture and maintain, and that provide good yields of products of interest, such as biofuels.